crash: checking hyper with borrowck-migrate

[matthiaskrgr]

git clone https://github.com/hyperium/hyper
cd hyper
git checkout v0.11.27
RUSTFLAGS="-Zborrowck=migrate" cargo check -j1

       Fresh nodrop v0.1.12
       Fresh cfg-if v0.1.4
       Fresh libc v0.2.42
       Fresh lazy_static v1.0.2
       Fresh scopeguard v0.3.3
       Fresh byteorder v1.2.4
       Fresh memoffset v0.2.1
       Fresh slab v0.4.0
       Fresh futures v0.1.23
       Fresh lazycell v0.6.0
       Fresh version_check v0.1.4
       Fresh scoped-tls v0.1.2
       Fresh smallvec v0.2.1
       Fresh safemem v0.2.0
       Fresh slab v0.3.0
       Fresh try-lock v0.1.0
       Fresh take v0.1.0
       Fresh language-tags v0.2.2
       Fresh percent-encoding v1.0.1
       Fresh arrayvec v0.4.7
       Fresh crossbeam-utils v0.3.2
       Fresh log v0.4.3
       Fresh iovec v0.1.2
       Fresh net2 v0.2.33
       Fresh rand v0.4.2
       Fresh num_cpus v1.8.0
       Fresh time v0.1.40
       Fresh tokio-executor v0.1.2
       Fresh tokio-service v0.1.0
       Fresh relay v0.1.1
       Fresh base64 v0.9.2
       Fresh crossbeam-epoch v0.4.3
       Fresh log v0.3.9
       Fresh want v0.0.4
       Fresh bytes v0.4.9
       Fresh mio v0.6.15
       Fresh rand v0.3.22
       Fresh futures-cpupool v0.1.8
       Fresh tokio-timer v0.2.4
       Fresh httparse v1.3.2
       Fresh crossbeam-deque v0.3.1
       Fresh tokio-io v0.1.7
       Fresh unicase v2.1.0
       Fresh tokio-threadpool v0.1.5
       Fresh tokio-reactor v0.1.2
       Fresh tokio-codec v0.1.0
       Fresh mime v0.3.8
       Fresh tokio-fs v0.1.2
       Fresh tokio-tcp v0.1.0
       Fresh tokio-udp v0.1.1
       Fresh tokio v0.1.7
       Fresh tokio-core v0.1.17
       Fresh tokio-proto v0.1.1
    Checking hyper v0.11.27 (file:///tmp/hyper)
     Running `rustc --crate-name hyper src/lib.rs --crate-type lib --emit=dep-info,metadata -C debuginfo=2 --cfg 'feature="default"' --cfg 'feature="server-proto"' --cfg 'feature="tokio-proto"' -C metadata=465f7886ca4a40ca -C extra-filename=-465f7886ca4a40ca --out-dir /tmp/hyper/target/debug/deps -C incremental=/tmp/hyper/target/debug/incremental -L dependency=/tmp/hyper/target/debug/deps --extern base64=/tmp/hyper/target/debug/deps/libbase64-7f888070408e9584.rmeta --extern bytes=/tmp/hyper/target/debug/deps/libbytes-926f4be38b0ef49a.rmeta --extern futures=/tmp/hyper/target/debug/deps/libfutures-3e034e8c4fadab05.rmeta --extern futures_cpupool=/tmp/hyper/target/debug/deps/libfutures_cpupool-3f3a8918cddf229d.rmeta --extern httparse=/tmp/hyper/target/debug/deps/libhttparse-7fa16ff1de6399dc.rmeta --extern iovec=/tmp/hyper/target/debug/deps/libiovec-10dda303b566010f.rmeta --extern language_tags=/tmp/hyper/target/debug/deps/liblanguage_tags-fedadc717cc3771f.rmeta --extern log=/tmp/hyper/target/debug/deps/liblog-81cb68337885c10e.rmeta --extern mime=/tmp/hyper/target/debug/deps/libmime-e6896d1a95033795.rmeta --extern net2=/tmp/hyper/target/debug/deps/libnet2-ab600f3287d3dca8.rmeta --extern percent_encoding=/tmp/hyper/target/debug/deps/libpercent_encoding-0c7a64ed7c39bd90.rmeta --extern relay=/tmp/hyper/target/debug/deps/librelay-8fa98676479e7181.rmeta --extern time=/tmp/hyper/target/debug/deps/libtime-98f6d9e519834157.rmeta --extern tokio_core=/tmp/hyper/target/debug/deps/libtokio_core-825ab810c0bbc020.rmeta --extern tokio_io=/tmp/hyper/target/debug/deps/libtokio_io-25fbcf6adf05ccf3.rmeta --extern tokio_proto=/tmp/hyper/target/debug/deps/libtokio_proto-22632b982b7a70d1.rmeta --extern tokio_service=/tmp/hyper/target/debug/deps/libtokio_service-bcd12f7a5bd6b195.rmeta --extern unicase=/tmp/hyper/target/debug/deps/libunicase-8cddf57e734c9821.rmeta --extern want=/tmp/hyper/target/debug/deps/libwant-fc7ca82b1f72e647.rmeta -Zborrowck=migrate`
thread 'main' panicked at 'scrape_region_constraints: incoming region obligations = [
    (
        NodeId(
            4242
        ),
        RegionObligation(sub_region=ReStatic, sup_type=B)
    )
]', librustc/traits/query/type_op/custom.rs:85:5
stack backtrace:
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
             at libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::print
             at libstd/sys_common/backtrace.rs:71
             at libstd/sys_common/backtrace.rs:59
   2: std::panicking::default_hook::{{closure}}
             at libstd/panicking.rs:211
   3: std::panicking::default_hook
             at libstd/panicking.rs:227
   4: rustc::util::common::panic_hook
   5: std::panicking::rust_panic_with_hook
             at libstd/panicking.rs:479
   6: std::panicking::continue_panic_fmt
             at libstd/panicking.rs:390
   7: std::panicking::begin_panic_fmt
             at libstd/panicking.rs:345
   8: <rustc::traits::query::type_op::custom::CustomTypeOp<F, G> as rustc::traits::query::type_op::TypeOp<'gcx, 'tcx>>::fully_perform
   9: rustc_mir::borrow_check::nll::type_check::type_check
  10: rustc_mir::borrow_check::nll::compute_regions
  11: rustc_mir::borrow_check::do_mir_borrowck
  12: rustc::ty::context::tls::with_related_context
  13: rustc::infer::InferCtxtBuilder::enter
  14: rustc_mir::borrow_check::mir_borrowck
  15: rustc::ty::query::__query_compute::mir_borrowck
  16: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::mir_borrowck<'tcx>>::compute
  17: rustc::ty::context::tls::with_context
  18: rustc::dep_graph::graph::DepGraph::with_task_impl
  19: rustc::ty::context::tls::with_related_context
  20: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::force_query_with_job
  21: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::get_query
  22: rustc::ty::query::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::mir_borrowck
  23: rustc_mir::borrow_check::nll::type_check::TypeChecker::check_stmt
  24: rustc_mir::borrow_check::nll::type_check::TypeChecker::typeck_mir
  25: rustc_mir::borrow_check::nll::type_check::type_check
  26: rustc_mir::borrow_check::nll::compute_regions
  27: rustc_mir::borrow_check::do_mir_borrowck
  28: rustc::ty::context::tls::with_related_context
  29: rustc::infer::InferCtxtBuilder::enter
  30: rustc_mir::borrow_check::mir_borrowck
  31: rustc::ty::query::__query_compute::mir_borrowck
  32: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::mir_borrowck<'tcx>>::compute
  33: rustc::ty::context::tls::with_context
  34: rustc::dep_graph::graph::DepGraph::with_task_impl
  35: rustc::ty::context::tls::with_related_context
  36: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::force_query_with_job
  37: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::get_query
  38: rustc::ty::query::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::mir_borrowck
  39: rustc::ty::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::par_body_owners
  40: rustc::util::common::time
  41: rustc::ty::context::tls::enter_context
  42: <std::thread::local::LocalKey<T>>::with
  43: rustc::ty::context::TyCtxt::create_and_enter
  44: rustc_driver::driver::compile_input
  45: rustc_driver::run_compiler_with_pool
  46: <scoped_tls::ScopedKey<T>>::set
  47: <scoped_tls::ScopedKey<T>>::set
  48: syntax::with_globals
  49: <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once
  50: __rust_maybe_catch_panic
             at libpanic_unwind/lib.rs:105
  51: rustc_driver::run
  52: rustc_driver::main
  53: std::rt::lang_start::{{closure}}
  54: std::panicking::try::do_call
             at libstd/rt.rs:59
             at libstd/panicking.rs:310
  55: __rust_maybe_catch_panic
             at libpanic_unwind/lib.rs:105
  56: std::rt::lang_start_internal
             at libstd/panicking.rs:289
             at libstd/panic.rs:392
             at libstd/rt.rs:58
  57: main
  58: __libc_start_main
  59: <unknown>
query stack during panic:
#0 [mir_borrowck] processing `<client::Client<C, B>>::send_request::{{closure}}`
#1 [mir_borrowck] processing `<client::Client<C, B>>::send_request`
end of query stack
error: internal compiler error: unexpected panic
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports
note: rustc 1.29.0-nightly (97085f9fb 2018-08-01) running on x86_64-unknown-linux-gnu
note: compiler flags: -Z borrowck=migrate -C debuginfo=2 -C incremental --crate-type lib
note: some of the compiler flags provided by cargo are hidden
error: Could not compile `hyper`.
Caused by:
  process didn't exit successfully: `rustc --crate-name hyper src/lib.rs --crate-type lib --emit=dep-info,metadata -C debuginfo=2 --cfg 'feature="default"' --cfg 'feature="server-proto"' --cfg 'feature="tokio-proto"' -C metadata=465f7886ca4a40ca -C extra-filename=-465f7886ca4a40ca --out-dir /tmp/hyper/target/debug/deps -C incremental=/tmp/hyper/target/debug/incremental -L dependency=/tmp/hyper/target/debug/deps --extern base64=/tmp/hyper/target/debug/deps/libbase64-7f888070408e9584.rmeta --extern bytes=/tmp/hyper/target/debug/deps/libbytes-926f4be38b0ef49a.rmeta --extern futures=/tmp/hyper/target/debug/deps/libfutures-3e034e8c4fadab05.rmeta --extern futures_cpupool=/tmp/hyper/target/debug/deps/libfutures_cpupool-3f3a8918cddf229d.rmeta --extern httparse=/tmp/hyper/target/debug/deps/libhttparse-7fa16ff1de6399dc.rmeta --extern iovec=/tmp/hyper/target/debug/deps/libiovec-10dda303b566010f.rmeta --extern language_tags=/tmp/hyper/target/debug/deps/liblanguage_tags-fedadc717cc3771f.rmeta --extern log=/tmp/hyper/target/debug/deps/liblog-81cb68337885c10e.rmeta --extern mime=/tmp/hyper/target/debug/deps/libmime-e6896d1a95033795.rmeta --extern net2=/tmp/hyper/target/debug/deps/libnet2-ab600f3287d3dca8.rmeta --extern percent_encoding=/tmp/hyper/target/debug/deps/libpercent_encoding-0c7a64ed7c39bd90.rmeta --extern relay=/tmp/hyper/target/debug/deps/librelay-8fa98676479e7181.rmeta --extern time=/tmp/hyper/target/debug/deps/libtime-98f6d9e519834157.rmeta --extern tokio_core=/tmp/hyper/target/debug/deps/libtokio_core-825ab810c0bbc020.rmeta --extern tokio_io=/tmp/hyper/target/debug/deps/libtokio_io-25fbcf6adf05ccf3.rmeta --extern tokio_proto=/tmp/hyper/target/debug/deps/libtokio_proto-22632b982b7a70d1.rmeta
--extern tokio_service=/tmp/hyper/target/debug/deps/libtokio_service-bcd12f7a5bd6b195.rmeta --extern unicase=/tmp/hyper/target/debug/deps/libunicase-8cddf57e734c9821.rmeta --extern want=/tmp/hyper/target/debug/deps/libwant-fc7ca82b1f72e647.rmeta -Zborrowck=migrate` (exit code: 101)

rustc 1.29.0-nightly (97085f9fb 2018-08-01)

[klemens]

I get (probably) the same ICE with the following code using itertools 0.7.8:

#![feature(nll)]

extern crate itertools;
use itertools::Itertools;

fn main() {
    vec![0]
        .into_iter()
        .group_by(|_| 0)
        .into_iter()
        .map(|_| 0);
}

The ICE happens on the first closure (the group_by one) with an identical backtrace and it does not crash without the map.

thread 'main' panicked at 'scrape_region_constraints: incoming region obligations = [
    (
        NodeId(
            23
        ),
        RegionObligation(sub_region='_#1r, sup_type=i32)
    )
]', librustc/traits/query/type_op/custom.rs:85:5
[…]
note: rustc 1.30.0-nightly (3edb355b7 2018-08-03) running on x86_64-unknown-linux-gnu
note: compiler flags: -C debuginfo=2 -C incremental --crate-type bin

[passy]

You beat me to the report. I ran into the same issue with group_by() and was trying to minimize the test case.

[klemens]

I tried to reduce this some more (especially removing itertools). This is the smallest example that I could come up with that still reproduces the ICE:

#![feature(nll)]

fn main() {
    S1 {}
        .into_iter()
        .map(|_| ());
}

pub struct S1 {}

pub struct S2<'a>
{
    phantom: &'a (),
}

pub struct S3<'a, I: 'a>
    where I: Iterator,
          I::Item: 'a,
{
    it: &'a I,
}

impl<'a> IntoIterator for &'a S1
{
    type Item = S3<'a, std::iter::Empty<()>>;
    type IntoIter = S2<'a>;

    fn into_iter(self) -> Self::IntoIter {
        S2 { phantom: &() }
    }
}

impl<'a> Iterator for S2<'a>
{
    type Item = S3<'a, std::iter::Empty<()>>;

    fn next(&mut self) -> Option<Self::Item> {
        None
    }
}

playground

[klemens]

And another round of minification, removing any dependency on std/core and two levels of structs. I guess it won't become much smaller:

#![feature(nll)]

fn main() {}

fn fail<'a>() -> Struct<'a, Generic<()>> {
    Struct(&Generic(()))
}

struct Struct<'a, T>(&'a T) where
    T: Trait + 'a,
    T::AT: 'a; // only fails with this bound

struct Generic<T>(T);

trait Trait {
    type AT;
}

impl<T> Trait for Generic<T> {
    type AT = T; // only fails with a generic AT
}

playground